At the office, Lionel is pursuing his hobby and pouring over clippings of the 40-year-old murder case of Sable Hill, a minor actress. E.L. isn't particularly interested. Lionel comes up with a theory and then stops E.L. from betting on the horses. The partners take to the streets and Lionel laments how modern murders are crude compared to the elegance of the Sable Hill murder. A car tries to run E.L. down and then the driver opens fire. E.L. avoids taking any damage, but has to admit he doesn't know anyone trying to kill him at the moment.
The investigating officer, Sgt. Bogart, is skeptical of E.L.'s claim that he's an innocent bystander. When Lionel objects and notes that E.L. has paid his debt to society, Bogart warns that criminals fight over the loot. E.L. insists that he's reformed. Once Bogart leaves, Lionel takes down his badge number to file a complaint and notes that Lt. Laws, the officer who handled the Sable Hill case, was retired with honors and wouldn't have acted that way. E.L. tells him to drop it and they go to a bar to relax. Lionel can't resist asking if E.L. might be on a con, and accepts E.L.s claim that he's innocent. When E.L. notes that he now leaves his marks clean, Lionel wonders if it's an older mark. E.L. figures that it is just a random shooting and Lionel can't come up with a better explanation. A number of beers later, the partners stagger home when the same people open fire on them again with machineguns. E.L. has to admit that there must be something going on.
Bogart comes to see E.L. and Lionel when they make a new report. He still believes that E.L. is involved in something and ignores E.L.'s protestations. As he leaves, Bogart notices that Lionel is working the Sable Hill case and admits that there aren't any crimes like that any more. Lionel wants to talk to Lt. Laws, but E.L. wants to handle it on their own. His partner insists that Laws is sharp and can help. That night, they stay at the office and Lionel stands watch, getting out his target pistol, while reading a Mark Savage detective novel. He's unaware that someone is planting explosives in Lionel's car.
The next morning, the partners go out the back but see a car come after them. They panic before realizing it's an old lady driving past. As they go to the car, Lionel wonders if he and Laws turned up something on the Sable Hill murder. He called Laws, who said he found something on one of the suspects, Jigs Duran. Lionel questioned Duran several days ago, and wonders if the killers are shooting at him and E.L. is just a bystander. He wants to warn Laws, and E.L. reluctantly agrees. E.L. insists in driving in the Mercedes Benz that he scammed, and Lionel checks his car and discovers that it's wired.
The partners walk to Laws' house and discover that the door is open. They burst in and find Laws with a shotgun. He explains that someone shot at him through the door and grazed him. Laws agrees that Lionel's theory is correct. When he goes to wash up, E.L. admits that they might have stumbled onto something. Lionel explains that a gun turned up at Hanson Dam, where Sable Hill's body turned up. However, the fingerprint card for the gun disappeared 40 years ago. He found it and gave the card to Laws, but Laws admits that he may have forgotten. He suggests they go to see Duran at his hotel where he's tracked him down, but realizes that E.L. is an ex-con. However, he admits that he'd rather have a criminal on his side and is happy to have E.L. along. As they leave, Laws tells his neighbor, Edna, to let the locksmith in. Lionel warns that Duran accused Laws of beating him, and probably won't talk to him. Laws admits that he beat Duran, and is disgusted with the modern-day bureaucracy.
At the hotel, Laws gets out a rubber hose as they ride up the elevator. He's eager to solve the case, and ready to beat Duran to get what he wants. As they get out of the elevator, they spot Duran and Vernon opens fire. They exchange shots and Duran gets away, and E.L. warns Lionel that Laws is nuts.
Bogart is called in and knows Laws. He talks privately and E.L. wonders if Laws is going to sell them out. Lionel is disappointed in his tarnished idol. Bogart takes Lionel's pistol and Laws warns that Lionel shouldn't carry it without a license. Lionel tells Laws that he's going to check on the fingerprint card himself, and Bogart wonders what's going on. Laws explains and Bogart wonders if he should take them in, but decides to cut them loose.
Back at the office, E.L. starts going over the Sable Hill case, but Lionel isn't interested at first. He finally goes back over his theories on the case and explains that most of the suspects died within two years, all of unnatural causes. He and Laws figured the deaths are all as reported. Duran is the one who told Lionel about the missing fingerprint card when he tracked the man down. Lionel remembers a lead on a mysterious admirer that the police never identified. E.L. wonders if Hill was a hooker because she had plenty of money but never got any movie roles. Lionel agrees that it's a possibility, and E.L. suggests that they get access to the computer files on unsolved cases. It takes E.L. six seconds to come up with an idea.
The partners go to a shop and buys a model of an Air Force fighter, then apply the decals to blank identification badges. They then go to the police station and pass themselves off as Air Force MPs from the Pentagon. They talk to Captain Matthews, the watch commander, who wants a close look at their badges. They ask for aspirin, but she has them in her desk. E.L. spills them and Lionel distracts her while E.L. makes a fake phone call. She finally relents and gives them access to the computer room. As they go downstairs, they notice Stephen J. Cannell, author of the Mark Savage novels. Before Lionel can get his autograph, they're forced to get out of the way of some officers. They then talk to Gail Strickland, the computer technician, and have her get them the files. She flirts with Lionel, almost making him blow his cover.
As they leave, they bump into Bogart and run. They duck into a break room, remove their jackets, and haul out a coffee vending machine. Once they're clear of the station, they drop it in the middle of the street, get to their car, and drive away before Bogart can catch them.
When they check the files, the partners discover that Sable Hill had a record as a prostitute, and Laws was the cop who busted her. She was killed two months later, and he headed the murder investigation. E.L. figures Law snarled up the investigation and beat Duran into silence, and lost the fingerprint card. Now Lionel has reopened the case, and Laws had to go along with him. Lionel figures that Laws has been stalling him all along.
The partners go to the office so they can get all of Lionel's files and find something on Laws. E.L. sends Lionel in first and then enters. The police haven't arrived yet,. Duran calls and says that Laws plans to kill him, and that he wants to meet Lionel at Hanson Dam. Lionel agrees, unaware that Laws forced him to make the call at gunpoint.
As Lionel and E.L. leave, the patrolmen arrive and the partners bluff their way past as police detectives. As they go, Lionel takes the dynamite out of his car and brings it with him, and they drive off just as Bogart arrives.
At Hanson Dam, Lionel wires himself with the dynamite and then goes to the boathouse where Sable Hill was found 40 years ago. There's no sign of Duran, While they wait, E.L. asks for one of the sticks of dynamite. Duran finally comes down the hill, and Laws opens fire. Duran tells them what is happening as they take cover. E.L. throws his stick of dynamite but it falls short and runs down the hill. They throw the second stick with similar results. The third time proves a charm and Laws is stunned long enough for them to disarm him.
Later, Lionel starts working the old Black Dahlia case as part of his hobby. E.L. would rather that he work crossword puzzles. When Lionel doesn't back down, E.L. goes outside and makes a fake phone call pretending to be Bogart. Lionel believes it until Bogart comes up behind him and arrests him for impersonating an officer.